|ALOHA||Algorithm that allows multiple terminals to share the same communication channel. Newly arriving packets are transmitted immediately. Packets are retransmitted if no acknowledgement is received. First used in Hawaii.|
|American Mobile Phone System||AMPS. |
U.S. Analog cellular phone system.
|analog modulation||(traditional) method of transmitting voice signals where the radio carrier wave is directly based on electrical voltages or currents caused by a user speaking into the microphone, or similar transmission of a signal which takes values from a continuous range of values as opposed to from a finite alphabet of values|
|base station||a land station at a fixed location supporting radio access by mobile users to a fixed communication infrastructure.|
|Bit Error Rate||BER. |
|burst||the physical (electric or electromagnetic) contents of a time slot|
|capture||successful transmission of a data packet despite interference from other terminals transmitting a conflicting signal. Occurs due to differences in received signal power, or signal separation properties of the receiver or the modulation method.|
|Code Division Multiple Access||CDMA. |
Multiple access method based on spread spectrum in which different users transmit on (approximately) the same carrier frequency, but use different spreading codes.
|cell||the area covered by radio signals from a base station, and in which a mobile station can successfully transmit to a base station|
|cellular network||Network in which frequencies are reused in a regular pattern, usually with basic area elements of hexagonal shape|
|cell sectorization||Splitting (theorectically hexagonal) cells into multiple independent sectors (typically 3) that each have their own transmit and receive facilities.|
|cell splitting||A method of increasing capacity by reducing the size of the cell.|
|circuit-switching||the allocation of network resources (link capacity, switches) for the entire duration of a communication session.|
|cluster size||number of different channels needed in a particular frequency reuse plan. Related to reuse distance.|
|coding||intentional replacement of a set of symbols by another set of symbols. Applications are detection or correction of errors, spectral shaping of the transmit signal, or confidentiality.|
|collision||conflicting simultaneous transmission by multiple terminals in a random access network.|
|coverage area||part of the area to which a transmitter gives satisfactory service|
|Carrier Sense Multiple Access||CSMA. |
listen before talk
|Cordless Telephone ..||CT-0, CT-1, CT-2. |
various generations of a cordless phone standard.
|Digital Audio Broadcasting||DAB. |
|Dynamic Channel Assignment||DCA. |
|Digital Communication System||DCS. |
1800 MHz version of GSM
|decibel||a ratio, expressed as ten times the base-10 logarithm of the ratio of two power levels. This is equivalent to 20 times the base-10 logarithm of the ratio of two voltage, field or current levels.|
|Digital Enhanced Cordless Telephone||DECT. |
previously: Digital European Cordless Telephone. Operates in 1800 MHz band.
|delay spread||parameter describing the frequency dispersion of a multipath channel. 1) total delay spread: time interval during which delayed reflected waves arrive. 2) rms delay spread: weighted value of interarrival times of reflected waves|
|digital modulation||A method of transmitting a signal over a radio carrier using symbols of an alphabet of finite size, such as the computer's binary 0s and 1s.|
|dispersion||variations in the channel transfer amplitude. Frequency dispersion: differences in channels response at different frequencies. Time dispersion: time variations of the channel response|
|diversity||technique of receiving a radio signal through multiple channels, to improve reliability|
|doppler spread||(one half times the) width of the spectrum of a received signal when a sinusoidal wave is transmitted over a time dispersive channel|
|downlink||Originally: A radio link from a satellite to a receiving site on earth or in an aircraft. Now also used for the (forward) link from base station to portable terminal.|
|Direct Sequence||DS. |
form of spread-spectrum in which the user signal is multiplied by a fast (spectrally broad) code sequence to increase the transmission bandwidth.
|Digital Short Range Radio||DSRR. |
system for short range communication. For in stance between a car and a roadside base station or gantry.
|duplex||Method of operating a network in which transmission is possible simultaneously in both directions of a telecommunications channel.|
|ERMES||Paging system, originally developed in Europe|
|equalization||signal processing (filtering) intended to undue channel dispersion. Mostly a compromise is made between combating channel dispersion and avoiding undesirable noise enhancements|
|erlang||unit of telephone traffic intensity.|
|European Telecommunications Standards Institute||ETSI. |
European organization responsible for establishing common industry-wide telecommunication standards.
|fading||Time variations of the signal strength received over a radio link. Fading occurs when the several reflected waves (destructively or constructively) interfere with each other.|
|Federal Communications Commission||FCC. |
|Frequency Division Multiple Access||FDMA. |
Multiple access method in which different users transmit at different carrier frequencies.
|flat fading||frequency-nonselective fading. Form of fading that does not cause intersymbol interference.|
|frequency modulation||FM. |
analog modulation method, exploiting variations in the instantaneuos carrier frequency
|Frequency Shift Keying||FSK. |
digital frequency modulation method
|free space loss||FSL. |
power loss due to the spreading of energy over the surface of a sphere as the signal travels away from the transmit source.
|Geosynchronous Earth Orbit||GEO. |
satellite communication system.
|GMSK||Digital phase (or frequency) modulation method, for instance used in GSM|
|GSM||previously Groupe de travail Speciale pour les services Mobiles. Widely used digital cellular phone standard, initiated in Europe.|
|handover||action of changing the handling the operation and control of a radio link from one base station to another as the user moves from one cell to another.|
|half duplex||communications system that supports conversation in two directions but not simultaneously by sharing a communication path between the two directions|
|Hertz||unit of measuring the frequency of a signal.|
|hidden terminal||terminal in a CSMA network actively transmitting data, but which is not noticed by another terminal with data ready for transmission.|
|Intelligent Network||IN. |
A secondary network used to create and deliver advanced services to subscribers to public telephone networks (fixed or mobile)
|in-phase component||component of a signal that has the same phase as a reference sinusoidal signal.|
|interference||signals from other emitters than from transmitter sending the wanted signal. Interference differs from noise in that interference often contains similar waveforms as the wanted signal|
|interleaving||intentional resequencing (shuffling) of the bits in a signal according to a predefined method known by both transmitter and receiver, to avoid burst errors.|
|IS-95||U.S. Cellular CDMA standard.|
|Industrial, Scientific and Medical||ISM. |
bands of the radio spectrum.
|Inhibit Sense Multiple Access||ISMA. |
random access scheme in which the central node broadcasts a busy signal to avoid that terminals start a conflicting transmission when it is receiving data
|International Telecommunication Union||ITU. |
|jamming||Deliberate radiation of electromagnetic energy with the intent to impair the use of electronic systems by the opponent or enemy. Jamming signals can be sinusoidal (CW), noise-like or broadband transmitters, specific deceptive signals that imitate messages.|
|Japanese Digital Cellular||JDC. |
now renamed PDC. Operates in the 900 MHz and 1.5 GHz band.
|Low Earth Orbiting||LEO. |
Satellite communication system
|matched filter||filter with impulse response which is the time inverse of the expected received waveform. Optimum form of detection in Linear Time-Invariant Additive White Gaussian Noise channel. Can also be implemented as a correlator.|
|maximum ratio combining||method of prefiltering and adding signals arriving through different branches of a diversity receiver. Follows the principle of the matched filter by weighing a signal proportionally to its amplitude.|
|microcell||cell with relatively small radius, typically a few hundreds of meters, typically used in a dense cellular network with many subscribers.|
|mobile station||a user terminal in a radio network intended to be used while in motion or during halts at unspecified points|
|Mobile Switching Center||MSC. |
Telecommunications node connecting and controlling several cellular base stations.
|multiple access||method that allows multiple spatially separated users to share the same communication channel to a common receiver.|
|multiplexing||method of combining multiple user signals in a telecommunications switch or base station|
|noise||random variations in output signal, due to natural of man-induced mechanisms.|
|noise temperature||ratio of the thermal noise power present in a system over the noise power that would be present a perfect system with only thermal noise, operating at 1 degree Kelvin.|
|narrowband||1. A radio signal whose bandwidth is smaller than the coherence bandwidth of the dispersive channel, or 2 . A radio signal whose bandwidth is on the order of its information bandwidth, as opposed to spread spectrum.|
|Nordic Mobile Telephone||NMT. |
Scandinavian analog cellular telephone system, at 450 or 900 MHz.
|Orthogonal Frequency Division Multiplex||OFDM. |
Multi-carrier modulation method with partially overlapping but nonetheless orthogonal subcarriers.
|outage||event during which the signal-to-noise or signal-to-interference ratio is insufficient to allow acceptable performance of the receiver|
|path loss||(average) propagation attenuation between transmitter and receiver. Depends on distance, antenna heights and atmospheric and terrain properties.|
|packet||message or a piece of a message, treated as an independent segment of data by the network.|
|packet switching||the assignment of network resources by splitting the information flow into packets. These are sent from node to node in the network without prior reservations|
|paging||Communication service that offers one-way transmission of short messages. Typically a paging device (pager) produces an audible 'bleep' when a message arrives.|
|Personal Communications Network||PCN. |
usually for short range radio communication but nonetheless with a cellular reuse lay-out. Acronym now often used for DCS 1800.
|Personal Communications Service||PCS. |
In the U.S., a band of a width of 120 MHz has been allocated in the near 1.9 GHz
|Personal Communications Service||PCS-1900. |
U.S. version of GSM, operating in the 1.9 GHz band.
|Personal Digital Cellular||PDC. |
Japanese cellular system.
|Phase modulation||PM. |
Method of modulating a base signal to create an RF signal by varying the phase on a (sinusoidal) carrier wave.
|propagation||natural mechanism of dissemination of radio energy|
|Phase Shift Keying||PSK. |
digital phase modulation.
|quadrature component||component of a signal that is orthogonal to (90 degrees out of phase with) a reference sinusoidal signal.|
|random access||method or algorithm that allows multiple terminals to share the same communication channel.|
|rake receiver||special form of a matched filter to detect direct-sequence spread-spectrum signals over a dispersive (multipath) channel. Optimally collects energy received over variously delay propagation paths.|
|rayleigh fading||fading characterized by a rayleigh probability density of the amplitude, thus an exponentially distributed power. Rayleigh fading typically occurs when an infinitely large number reflected waves with i.i.d. amplitude and amplitude cumulate|
|Radio Data (Broadcast) System||RDS, RDBS. |
method to add a data signal to an FM broadcast signal by subcarrier modulation (57 kHz).
|reuse||assignment of the same frequency channel in multiple areas, and simultaneous use of these channels allowed by propagation losses between spatially separated areas|
|reuse distance||distance between the centers of two cells using same frequency channel.|
|rician fading||fading characterized by a rician probability density of the amplitude. Rician fading typically occurs when a dominant component (say a line-of-sight) plus an infinitely large number reflected waves with i.i.d. amplitude and amplitude cumulate|
|Radio Frequency||RF. |
In radio communication baseband signals (voice or data) are modulated onto a carrier and before transmission. Hence, the signal spectrum is shifted to a band where propagation and interference conditions are appropriate.
|scattering||dispersion of radio energy caused by reflections|
|service area||area in which a mobile station can be reached or from where a mobile station can initiate a communication session. Typically includes the coverage areas of multiple cells|
|simplex||method of operating a network in which transmission is possible only in one direction. No return channel available.|
|smart antenna||array of antenna elements and associated signal processing, used to improve the performance and to minimize the effect of interference.|
|spread spectrum||transmission and modulation method that intentionally spreads a signal bandwidth over a wide bandwidth|
|Total Access Communication System||TACS. |
analog cellular telephone system in the United Kingdom and Japan, using 25 kHz NBFM channels
|Time Division Multiple Access||TDMA. |
Multiple access method in which different users transmit in different time intervals.
|Trans European Trunked Radio Access||TETRA. |
European digital cellular landmobile radio system for closed user groups
|Telecommunications Industry Association||TIA. |
|thermal noise||random variations in output signal, due to the natural mechanism of motion of electrons.|
|trunk||in a telephone network, the connection between the switches carrying multiple voice circuits|
|trunking||use of the radio spectrum in which multiple user groups share the same channels using an automatic multiple access mechanism, thus gaining efficiency|
|uplink||Originally: A radio link from a site on the earth or from an aircraft to a satellite. Now also used for the (reverse) link from mobile user terminal to base station.|
|vocoder||Voice coder in which speech is heavily compressed to reduce the channel bit rate required to transmit speech typically to a few hundreds of bits per second|
|Very Small Aperture Terminal||VSAT. |
a small mobile or portable satellite communication terminal using small diameter dish antenna.
|Vector Sum Excited Linear Predictive||VSELP. |
Commonly used method for speech coding
|Wireless Local Area Network||WLAN. |
Typically using spread-spectrum transmission in the 2.4 GHz or 5.8 GHz ISM band.
|Wireless Local Loop||WLL. |
The application of radio communication instead of copper wire provide the standard public telephone service.
Displayed: 114 entries in this glossary.